In order to improve operating characteristics of a semiconductor device, many attempts to improve resistance are being made. One approach has been to improve contact resistance between silicide and a silicon substrate.
The most important features of the contact resistance include a work function of silicide and a doping concentration of a silicon substrate because a Schottky barrier height (SBH) is determined by the work function and the doping concentration and the contact resistance is determined by the SBH.
As an example, when silicide of NiSi2 phase is formed in NMOS, the SBH of the PMOS can be relatively increased and resistance can be increased. If PMOS is applied in an eSiGe process, agglomeration of silicide can be generated. Therefore, performance of the semiconductor device can be decreased, and leakage of the device can be increased.